PMC:103662 / 20524-21344 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/103662","sourcedb":"PMC","sourceid":"103662","source_url":"https://www.ncbi.nlm.nih.gov/pmc/103662","text":"The difference in pH dependence between the pR and bR photocycles can likely be attributed to differences in the microenvironment of the Schiff base, and is perhaps related to absence of Glu194/204 in pR. These adaptive differences presumably optimize the proteins to operate at maximum efficiency in the niches that their respective organisms occupy. In the case of the λ-proteobacteria, which in the open ocean (pH 7.8–8.0) occupy a signficantly more alkaline environment than halobacteria, perhaps the proton-release group is simply not under any evolutionary pressure to be capable of deprotonating in the M state at neutral pH. In this view, the principal role of E194 and E204 in bR may to modulate the pKa of the H+-release group in the M state to a value lower than the pH of the organism's external environment.","tracks":[]}